Pre-made spaceships?

[Rupert]

Originally Posted by thtraveller

2 or even 3 layers of armor and some ECM are appropriate on small military craft.

That leaves very little space for anything else however - clearly a design philosophy favouring defence over manoeuvre or offence.

[Rupert]

Originally Posted by thtraveller

For short duration fighters/craft you could go with non-superscience High-thrust Antimatter Thermal Rockets and the fuel is way cheaper. Antimatter catalyzed hydrogen is only $20K/ton rather than 12M$/ton for full antimatter engines.

Their DV per tank is not very impressive, however. In fact, if you're down at that level HEDM chemical rockets might be a better bet. The drives are cheaper, the fuel is much cheaper, and they give good acceleration.

Here's my attempt at a thrown together TL10, nosuperscience fighter:

SM+5 (30 tons)

Front:
[1-2] Armour, Nanocomposite (dDR14), Hardened
[3] Defensive ECM
[4-5] Fuel Tank - HEDM
[6]Weapon, Spinal Mount
[Core] Control Room (Pilot)

Centre:
[1] Armour, Nanocomposite (dDR7), Hardened
[2] Defensive ECM
[3-6] Fuel Tank - HEDM
[Core]Weapon, Spinal Mount: launcher, 24cm, 7 rounds

Rear:
[1] Armour, Nanocomposite (dDR7), Hardened
[2] Weapon, Spinal Mount
[3] Defensive ECM
[4-5] Fuel Tank - HEDM
[6]Reaction Engine, HEDM Rocket

She'll do 2Gs, has 4.8 mps DV (which is actually less than 7 minutes fuel). The price is $2.76M, a full load of fuel is $63K, and the missiles are $2.333M for conventional ones. The missiles are large enough that even cruiser (SM+10 or SM+11, IMO) armour should be vulnerable to conventional warheads.

More DV can be gained by replacing the spinal launcher with a large one and using the space for fuel tanks giving 7 mps DV (and such a design, were it streamlined, could reach orbit from Earth's surface), maybe a large beam weapon plus power plant and only 6.3 mps fuel, or maybe a second engine for 4G acceleration.

Anyway, what we have is a small, high acceleration fighter, with a single large missile system with enough DV for work in orbital space or similar. If more DV is desired acceleration will drop significantly and/or other systems will have to go (and ECM and armour are really the only dispensable systems), or a bigger vessel will be required.